Turbulent Flows of Kerosene, Water, and Air through Copper Ducts with Variable Outlet Geometries: Insight into Turbulent-Mixing, Stress-Redistribution, Pressure-Losses, Secondary-Flows, and Energy-Dissipation

Studying turbulent mixing, stress redistribution, pressure losses, secondary flows, and energy dissipation enhances industrial process efficiency, improves equipment durability, minimizes operational costs, optimizes fluid transport systems, supports design and promotes energy conservation. However, little is known about the influence of outlet geometry on turbulence characteristics (i.e. turbulent kinetic energy, turbulent intensity, effective viscosity , and effective thermal conductivity) in air, water, and kerosene flowing through Y-shaped copper ducts featuring regular, converging, and diverging outlets. A hybrid geometric configuration incorporating angular inlets and asymmetric outlets enables detailed analysis of turbulent mixing, stress redistribution, pressure losses, and secondary flow development in complex internal flow regimes. Numerical simulations were conducted using ANSYS Fluent 2023 R2, employing the shear stress transport (SST) turbulence model for accurate resolution of adverse pressure gradients and boundary-layer effects. High-quality meshing, grid independence validation, and robust solver configurations ensured numerical reliability and convergence. The results demonstrate that outlet geometry significantly influences turbulence intensity, effective viscosity, and thermal conductivity across different working fluids. For air, increasing inlet velocity enhances turbulent kinetic energy and turbulence intensity at the regular outlet, while the diverging outlet exhibits peak turbulence at higher cold-fluid velocities. In water flows, the converging outlet shows substantial turbulence growth under increased velocity conditions, highlighting the role of geometric restriction in enhancing mixing and energy dissipation. For kerosene, the regular outlet achieves maximum effective thermal conductivity due to improved fluid interaction and turbulence under elevated velocity conditions, whereas the diverging outlet exhibits lower viscosity as a consequence of geometric flow dispersion. Overall, the findings underscore the critical role of outlet configuration in determining turbulence behavior and thermal-fluid transport characteristics.